Enhancement of antibody dependent cellular cytotoxicity (ADCC) by combination of cytokines

Monoclonal antibodies (MAb) specific for tumor-associated antigens (TAA) ca n induce an immunological cellular attack of tumor cells by a process terme d antibody dependent cellular cytotoxicity (ADCC). Cytokines may augment AD CC by direct activation of immune cells or by enhancement of TAA on tumor c ells. Thus, we investigated whether ADCC by MAb 17-1A and BR55-2, which rec ognize TAA on colorectal tumor cells, can be augmented by 3-day incubation with different concentrations of IL-2, IL-4, IL-6, IL-12, IFN-alpha, IFN-ga mma,GM-CSF, M-CSF, and TNF-alpha. ADCC was assessed by a new flowcytometric cytotoxicity assay (Flieger et al. Immunol Methods 1995; 180:1-13) using P KH-2 labeled HT29 cells as targets and PKH-26 labeled peripheral blood mono nuclear cells from three healthy volunteers as effector cells. We found thr ee reaction patterns with the cytokines tested: (a) cytokines, which increa se ADCC (IL-2, IL-12, IFN-alpha and IFN-gamma, which represent Th1 cytokine s); (b) cytokines with no effect (GM-CSF, M-CSF, and TNF-alpha); and (c) cy tokines, which decrease ADCC (IL-4 and IL-6, which represent Th2 cytokines) . Then, we tested cytokines that increase ADCC in combination with the othe r cytokines. We found that the combinations IL-2/IFN-alpha, IL-2/IFN-gamma, IL-2/IL-12, and IL-12/IFN-alpha potentiated ADCC. By contrast, IL-4 reduce d the IL-2, IL-12, and IFN-alpha-induced ADCC. Since the Th1 response, coop eration of monocytes and CD4 cells is involved, we plan to elucidate by mag netic cell sorting (MACS) separation techniques, which cells are involved i n cytokine-induced ADCC. Our results may be useful for finding combinations of cytokines and MAb for the locoregional treatment of colorectal cancer.